Elaboration of geopolymer package derived from uncalcined phosphate sludge and its solidification performance on nuclear grade resins loaded with 134Cs.

Nuclear-grade Spent Organic Resin (SOR) contains high concentrations of radioactive nuclides and metal contaminants, while phosphate sludge contains high amount of fine clayey particles and CO32-, both posing a major threat to the biosphere. In this study, a novel geopolymer package (GP) was proposed to directly solidify SOR loaded with 134Cs by incorporating uncalcined phosphate sludge (UPS) as feedstocks, activated by NaOH/KOH. The results showed that alkali-mixed reagents-activated GP is more advantageous in terms of chemical stability and mechanical properties than NaOH-activated GP, recording compressive strength values greater than the waste acceptance criteria and OPC. The 28-day compressive strength of solidified packages can exceed 31 MPa at the highest amount of 42 wt% UPS. The addition of NaF powder into the solidified packages generates more hybrid type gels, which are more conducive to partial dissolution and bonding UPS particles, thereby producing stable and stronger GP. Leaching results of solidified GP in presence of up to 13 wt% SORs showed that only 0.15 % of total 134Cs was leached, even under aggressive solutions. Solidification mechanism revealed that activation of UPS-MK blend forms N,K-A-S-H, (N,K,C)-A-S-H/C-S-H gels coexisting with unreacted particles, thereby solidify/stabilize metal contaminants and Cs+ by a synergetic immobilization action of hydration products via substitution and encapsulation. This study provides a promising paradigm for effective solidification of nuclear-grade resins and synergetic harmless treatment of industrial/phosphate mine solid wastes.

Chitin-Based Magnesium Oxide Biocomposite for the Removal of Methyl Orange from Water.

In this work, a cost-effective chitin-based magnesium oxide (CHt@MgO) biocomposite with excellent anionic methyl orange (MO) dye removal efficiency from water was developed. The CHt@MgO biocomposite was characterized by FT-IR, XRD, SEM-EDX, and TGA/DTG. Results proved the successful synthesis of CHt@MgO biocomposite. Adsorption of MO on the CHt@MgO biocomposite was optimized by varying experimental conditions such as pH, amount of adsorbent (m), contact time (t), temperature (T), and initial MO concentration (Co). The optimized parameters for MO removal by CHt@MgO biocomposite were as follows: pH, 6; m, 2 g/L; t, 120 min. Two common isotherm models (Langmuir and Freundlich) and three kinetic models (pseudo-first-order (PFO), pseudo-second-order (PSO), and intraparticle diffusion (IPD)) were tested for experimental data fitting. Results showed that Langmuir and PFO were the most suitable to respectively describe equilibrium and kinetic results on the adsorption of MO adsorption on CHt@MgO biocomposite. The maximum Langmuir monolayer adsorption capacity (qm) on CHt@MgO biocomposite toward MO dye was 252 mg/g at 60 °C. The reusability tests revealed that CHt@MgO biocomposite possessed high (90.7%) removal efficiency after the fifth regeneration cycle.

Development and Characterization of Phosphate Glass Fibers and Their Application in the Reinforcement of Polyester Matrix Composites.

This study focused on the production and characterization of phosphate glass fibers (PGF) for application as composite reinforcement. Phosphate glasses belonging to the system 52P2O524CaO13MgO (11-(X + Y)) K2OXFe2O3YTiO2 (X:1, 3, 5) and (Y:0.5, 1) were elaborated and converted to phosphate glass fibers. First, their mechanical properties and chemical durability were investigated. Then, the optimized PGF compositions were used afterward as reinforcement for thermosetting composite materials. Polyester matrices reinforced with short phosphate glass fibers (sPGF) up to 20 wt % were manufactured by the contact molding process. The mechanical and morphological properties of different sPGF-reinforced polyester systems were evaluated. The choice between the different phosphate-based glass syntheses (PGFs) was determined by their superior mechanical performance, their interesting chemical durability, and their high level of dispersion in the polyester matrix without any ad sizing as proven by SEM morphological analysis. Moreover, the characterization of mechanical properties revealed that the tensile and flexural moduli of the developed polyester-based composites were improved by increasing the sPGF content in the polymer matrix in perfect agreement with Takayanagi model predictions. The present work thus highlights some promising results to obtain high-quality phosphate glass fiber-reinforced polyester parts which can be transposed to other thermosetting or thermoplastic-based composites for high-value applications.

Micro- and nano-structures of cellulose from eggplant plant (Solanum melongena L) agricultural residue.

Currently, agriculture sector produces enormous quantity of residues, creating severe environmental problems. These agricultural residues are rich in lignocellulosic fibers, making them sustainable sources to produce high added-value materials. This investigation aims to transform the eggplant plant residue (EPR) into purified cellulose microfibers (CMF) and cellulose nanocrystals (CNC). CMF with a yield of 54 %, diameter of 13.6 µm and crystallinity of 71 % were successfully obtained from raw EPR using alkali and bleaching treatments. By subjecting CMF to phosphoric and sulfuric acid hydrolysis, phosphorylated (P-CNC) and sulfated (S-CNC) were produced. P-CNC and S-CNC exhibited an aspect ratio of 89.4 and 74.2, zeta potential value of - 39.4 and - 28.7 mV, surface charge density of 116.7 and 218.2 mmol/kg cellulose and a crystallinity of 73 % and 80 %, respectively. Herein, the obtained cellulosic structures with excellent properties could be used in various applications, such as bio-derived fillers for polymer composites development.

Stipa tenacissima L.: A New Promising Source of Bioactive Compounds with Antioxidant and Anticancer Potentials.

BACKGROUND: Stipa tenacissima L. (S. tenacissima), called Esparto grass, is a cultivated species used for industrial purposes, including textile production. This species has never been studied for its medical potential before, nor has it been used in traditional medicines. It is thus fitting that the present study aimed to investigate the pharmacological potential of S. tenacissima. To achieve this goal, this work was conducted to study the chemical composition, antioxidant properties, and antiproliferative effects of S. tenacissima against cancerous cell lines, including the human colorectal adenocarcinoma cell line (HT-29) and human breast adenocarcinoma cell line (MDA-MB-231). Fractionation and characterization of S. tenacissima extract showed the presence of promising bioactive fractions. The fractions obtained from S. tenacissima extract exhibited interesting antioxidant properties, with IC50 values ranging from 1.26 to 1.85 mg/mL. All fractions, such as F1, F2, F3, and F4, induced an important antiproliferative effect on the cancer cell lines MDA-MB-231, scoring IC50 values ranging from 63.58 ± 3.14 to 99.880 ± 0.061 µg/mL. These fractions (F1, F2, F3, and F4) also exhibited a potent antiproliferative effect versus HT-29 cell lines, with IC50 values ranging from 71.50 ± 4.97 to 87.500 ± 1.799 µg/mL. Therefore, S. tenacissima could constitute a new natural source of bioactive compounds that can be used for therapeutic purposes to fight cancer and free radical damage.

Entrapment of organic fluorophores in calcium phosphate nanoparticles with slow release.

Two organic fluorophores, fluorescein (F) and rhodamine B (Rd), were entrapped in calcium phosphate nanoparticles. The as-obtained nanoparticles can be used for biological release applications. For this aim, calcium phosphate nanoparticles were synthesized using the precipitation method. Structural analysis of these nanoparticles was performed using XRD, FTIR, and Raman spectroscopy, confirming that the synthesized nanoparticles were hydroxyapatite. TEM and SEM analyses demonstrated that these nanoparticles had a size of 20 nm and a well-defined morphology. F and Rd (about 0.5 wt.%) were entrapped in these nanoparticles and their release, as a function of time, was studied via UV-Vis spectroscopy. The obtained results showed that the release of both fluorophores was progressive over time. The trapping efficiencies of the fluorophores were 67.15% and 90.76% for F and Rd, respectively.

Characteristics of sulfated and carboxylated cellulose nanocrystals extracted from Juncus plant stems.

In this study, sulfated and carboxylated cellulose nanocrystals (CNC) have been produced from newly identified cellulose-rich bio-sourced material, namely Juncus plant. The Juncus plant stems were firstly subjected to chemical treatments to produce purified cellulose microfibers (CMF) with an average diameter of 3.5 µm and yield of 36%. By subjecting CMF to sulfuric and citric/hydrochloric mixture acids hydrolysis, sulfated CNC (S-CNC) and carboxylated CNC (C-CNC) have been produced with a diameter of 7.3 ±â€¯2.2 and 6.1 ±â€¯2.8 nm, and a length of 431 ±â€¯94 and 352 ±â€¯79 nm, respectively. These newly extracted S-CNC and C-CNC exhibited a crystallinity of 81% and 83% with cellulose I structure and showed high thermal stability (>200 °C). Herein, this newly identified Juncus plant, which is a naturally-derived source, could be used as a valuable alternative to conventional sources such as wood and cotton for nanocellulose production. We speculate that the determined high thermal stability, the large aspect ratio and high crystallinity will allow the use of the extracted CNC as nano-reinforcing agents in polymers that require processing temperatures of up to 200 °C. Owing to their surface functionalities (sulfated or carboxylated surface groups), the here produced CNC could be used as nano-additives or nano-reinforcing agents for water-soluble bio-polymers in order to produce bio-nanocomposites by solvent casting techniques.

Improved mechanical properties of k-carrageenan-based nanocomposite films reinforced with cellulose nanocrystals.

This work investigates the isolation of cellulose nanocrystals (CNC) from sugarcane bagasse (SCB) waste and the evaluation of their mechanical reinforcement capability for k-carrageenan biopolymer. The results from Atomic Force Microscopy and Transmission Electron Microscopy indicated the successful extraction of CNC from SCB following alkali, bleaching and acid hydrolysis treatments. The CNC displayed a needle-like structure with an average aspect ratio of 55. The surface functionality of the CNC was evaluated by Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy measurements. X-ray diffraction studies showed that the as-extracted CNC exhibit cellulose I crystalline structure, with a crystallinity index of 80%. The obtained CNC were dispersed into k-carrageenan biopolymer matrix at various CNC contents (1, 3, 5 and 8 wt%) and the prepared films were further characterized. The incorporation of CNC decreased the light transmittance values but enhanced the mechanical properties compared with the neat k-carrageenan film. Empirical Halpin-Tsai model was used to predict the CNC dispersion within k-carrageenan matrix. The obtained nanocomposite films have the potential to be used as food packaging material.

Production of cellulose nanocrystals from vine shoots and their use for the development of nanocomposite materials.

In the present work, cellulose nanocrystals (CNC) were produced from vine shoots waste using chemical treatments followed by acid hydrolysis process. FTIR analysis confirmed that the non-cellulosic components were progressively removed during the chemical treatments, and the final obtained materials are composed of pure cellulose. AFM and TEM observations showed that the extracted CNC possess a needle-like shape with an average length of 456 nm and an average diameter of 14 nm, giving rise to an average aspect ratio of about 32. The as-extracted CNC exhibit a cellulose I structure with high crystallinity index (82%), as determined by XRD characterization. Importantly, the resulted CNC provide a higher thermal stability in comparison with CNC extracted from other resources, using the same extraction process. The isolated CNC's surface charge density was evaluated by XPS analysis and resulted in ~2.0 sulfate groups per 100 anhydroglucose units. In order to identify the reinforcing ability of the new extracted CNC, Carboxymethyl cellulose nanocomposite films were prepared with various CNC contents (1, 3, 5, 8 wt%) and their mechanical properties were investigated by uniaxial tensile test. The results showed that the as-extracted CNC displayed a higher reinforcing ability for nanocomposite materials.